It is common to provide a wellhead of a hydrocarbon well with ports allowing the mounting of devices for monitoring the annuli of the well. For example, such a device is disclosed in WO 2013/056857 A1, which is hereby incorporated by reference. Generally, a system for monitoring an annulus via a wellhead port comprises a plug body which is positioned in the port and comprises at least one sensor for measuring and monitoring at least one parameter in the annulus, e.g. pressure or temperature. In addition to provide a measuring or monitoring function, the plug body must provide a sealing function to prevent leakage to or from the annulus.
US 2012/012341 A1 discloses a wellhead port plug assembly comprising a first plug body which is arranged in an outlet port of the wellhead. The plug assembly further comprises a spool which is aligned with the outlet port. A second plug body is arranged in the spool. The first and second plug bodies can be removed from the well head assembly via the spool upon removal of a blind flange from the spool.
WO 2001/57360 A1 discloses a well data monitoring system which enables annulus pressure and other well parameters to be monitored in the outer annuli of the well casing program without adding any pressure containing penetrations to the well system.
WO 2006/061645 A1 discloses a plug retrieval and installation tool comprising a housing that is lowered on a lift line or riser and connected to subsea production equipment. A plug manipulator which can be extended to install, or retracted to retrieve, a plug-type barrier, is detachably mounted to the housing so that it can be retrieved independently of the housing. The installation tool eliminates the need for full-size intervention vessels or drilling rigs for plug retrieval/installation.
Furthermore, when not utilised for monitoring and measuring purposes, the port must be blocked in order to prevent leakage. This is normally accomplished by positioning a blind plug in the port such that the port is blocked. A blind plug is basically a plug body having no other purpose than to provide a sealing or plugging function.
A problem related to plug bodies positioned in wellhead ports of a hydrocarbon producing well, is that the well need normally to be taken out of production if the plug body is to be replaced. For example, a plug body may occasionally leak, in which case the plug body may need to be substituted for a new plug body. Also, it may be desirable to deploy a monitoring or measuring system in a previously unused port, in which case the blind plug needs to be removed and a plug body comprising a sensor needs to be positioned in its place.
In prior art plug assemblies, the well normally needs to be taken out of production in order for the plug body in the port to be replaced. This, of course, is a major disadvantage in a business where well uptime is paramount.
The present invention addresses this problem and seeks to provide a wellhead port plug assembly and a method allowing replacement of a plug body without having to take the well out of production.